Morphological and Molecular Characterization of Alternaria solani and Phytophthora infestans Isolates from Tomato Farms in Kenya

L.G. Mugao, P.W. Muturi, B.M. Gichimu and A.K. Kamiri

Background and Objective: Early and late blight caused by Alternaria solani and Phytophthora infestans respectively, are the world’s most important diseases of tomato. The objective of the study was to assess the morphological and molecular diversity of A. solani and P. infestans in tomato growing farms in Kirinyaga, Kenya. Materials and Methods: Infected tomato leaf samples were obtained from tomato farms and cultured using V8 Agar for P. Infestans and PDA for A. solani to facilitate isolation of the pathogens. The isolates were then subjected to morphological characterization using microscopic and macroscopic features and molecular characterization through PCR amplification of their ITS regions. The PCR products were then sequenced and blasted using NCBI database. Results: The results showed high morphological and molecular diversity within A. solani but low genetic variability within P. infestans. At least four clones of A. solani were found to exist in the study area but only one strain of P. infestans was identified. Other disease-causing pathogens were also isolated from the samples including A. alternata, a fungus that causes leaf spot and other diseases in plants and Fusarium equiseti, a soil-borne fungus that causes wilt disease in different vegetable plants. Conclusion: These findings are useful in the development of sustainable strategies to manage the early and late blight and other related diseases in tomato growing areas in Kenya.

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